Photochemical 3D fabrication methods produce fabricated 3D articles by performing photochemical fabrication using a photocurable resin composition. The methods are based on data input in three-dimensional CAD and are widely employed due to the fact that the target 3D fabricated object can be manufactured at high dimensional accuracy without creating a mould or the like.
As the photochemical 3D fabrication method, it has been widely adopted to selectively irradiate a liquid surface of a liquid-form photocurable resin composition which is introduced into a container (the fabrication tank for holding the photocurable resin composition) with light. Irradiation is controlled by a computer in a specified drawn pattern and curing is effected to a specified thickness resulting in a first layer. On the top of a first layer a second cured layer is created. The second layer comprises the same liquid resin layer as the first layer and is cured to a specified thickness by selective irradiation with light in the same way as the first layer. This layering process of forming cured layers produces a fabricated 3D object.
However, while the above conventional photochemical fabrication method has the advantage of producing fabricated 3D objects of outstanding accuracy regarding form and dimension, it has the disadvantage that a storage container (the fabrication tank) for holding a large amount of photocurable resin composition is necessary. The scale of the equipment is increased and in addition the amount of employed photocurable resin composition is raised. Further, it is difficult to produce multi-coloured fabricated 3D objects or fabricated 3D objects with different properties such as different hardness in different parts.
To overcome these drawbacks a photochemical 3D fabrication method based on the inkjet system has been developed (see JP-T-2003-535712). Such a method requires only small scale equipment and enables multi-coloured fabricated 3D objects or fabricated 3D objects having different hardness, or other properties, in different parts. Further only low quantities of photocurable resin are needed during the production.
In photochemical 3D fabrication using the inkjet method, fine droplets of a liquid-form photocurable resin composition are discharged from nozzles onto a base plate in a specified drawn pattern based on data input in 3D CAD, followed by light irradiation to effect curing. Then, further fine droplets of the liquid-form photocurable resin composition are discharged thereon from the nozzles in a specified drawn pattern, producing a superimposed layer, followed again by light irradiation. The repetition of this operation finally leads to a fabricated 3D object.
In both cases, the aforedescribed conventional photochemical 3D fabrication method in which the surface of the liquid-form photocurable composition held in the fabrication tank is irradiated with light of specified pattern to produce a fabricated 3D object and the photochemical 3D fabrication method employing the inkjet method, the fabricated 3D object may show distortion due to, for example, the self-weight of the 3D body during fabrication or following fabrication (for example, a fabricated 3D object having an overhang region, etc.). Further, distortion or the like readily occurs due to the influence of the heat associated with the light irradiation. Hence, support regions connected to the main body (the final fabricated 3D object) are also formed along with the main body at the time of the photochemical fabrication process in order to prevent such distortion to the main body.
In the aforesaid conventional photochemical 3D fabrication method in which the surface of the liquid-form photocurable composition held in the fabrication tank is irradiated with light of specified pattern to produce a fabricated 3D object, the photochemical fabrication is carried out using a single type of photocurable resin composition held in the fabrication tank. The support regions are formed from the same material as the main body and at the end of the photochemical fabrication process is removed from the main body by a mechanical means such as cutting, machining or abrading.
Using the inkjet method, the support regions may also be removed from the fabricated 3D object obtained by photochemical fabrication using a mechanical means such as cutting or machining (see JP-T-2003-535712). However the inkjet method provides the possibility to carry out photochemical fabrication by discharging fine liquid droplets of different photocurable resin compositions having different properties from the nozzles. There have been proposed techniques in which the main body is formed using a photocurable resin composition which produces a water-insoluble cured product and where the support regions are formed using a photocurable resin composition which produces a water-soluble cured product (see JP-A-10-155889 and JP-A-2012-111226).
The technique described in JP-A-10-155889 relates to a photocurable resin composition for forming the support regions employed in a photochemical fabrication method based on the inkjet method. The photocurable resin composition contains (A) 15-99 mass % of an acrylamide-based compound having one vinyl group, (B) 0.1-5 mass % of chain transfer agent and (C) 0.5-10 mass % of photopolymerization initiator, optionally along with (D) (meth)acrylate compound having at least two (meth)acryloyl groups and an aliphatic polyether structure or an aliphatic polyester structure, and/or (E) a non-curable compound of theoretical molecular weight no more than 500 having two or more hydroxyl groups. This photocurable resin composition chiefly comprises a (meth)acrylamide compound having one (meth)acryloyl group. By adding the chain transfer agent, the molecular weight is controlled and water solubility secured. The required mechanical properties as a support region are obtained by optionally using component (D) [(meth)acrylate compound of functionality two or more] in this photocurable resin composition. However, the water solubility of the support regions following photocuring is insufficient and the photochemically fabricated object needs to be immersed in water for a long time in order to eliminate the support regions from the main body.
The technique described in JP-A-2012-111226 relates to a photocurable resin composition for forming the support regions employed in an inkjet photochemical fabricating method. The resin composition contains water-soluble monofunctional ethylenically-unsaturated monomer, alkylene oxide adduct containing oxypropylene groups, and/or water, together with a photopolymerization initiator. This photocurable resin composition forms support regions which readily dissolve in water. However, the photocuring performance is inadequate, and the supporting performance of the support regions formed by the photocuring is also unsatisfactory.